Grab sampler

Abstract

This invention relates to a grab sampler for liquids especially for crude oil flowing through pipelines. The sampler has a set of concentric tubular members including an outer body with an inlet and outlet, and a sleeve and a hollow piston which are respectively axially slideable within the body and the sleeve. The piston has an internal non-return valve as its base. The sleeve, the piston base and the body are capable of defining a sample chamber so as to trap a sample of the liquid flowing through the pipeline. Application of pressure on the piston displaces the trapped sample through the nonreturn valve to the inside of the piston and is recovered therefrom by sample removal means.

I claim: 
     
       1. A device for sampling liquid flowing through a pipeline, said device being adapted to be inserted into the pipeline and comprising: A. a set of concentric tubular members made up of (1) an outer, hollow cylindrical body having a base closing one end thereof and having a radially oriented liquid inlet and liquid outlet adjacent to the base thereof,   (2) a sleeve mounted within and axially slideable with respect to the outer cylindrical body, and   (3) a hollow piston mounted within and axially slideable with respect to the sleeve, wherein (a) the sleeve is adapted to define a liquid-tight chamber between the walls thereof, the base portion of the body and the piston, and is capable of trapping a sample of liquid within said chamber,   (b) the piston is provided at the base thereof with an internal non-return valve and is adapted to apply pressure to the trapped sample thereby displacing the sample through the valve into the inside of the piston, and   (c) the inside of the piston is connected to sample removal means for removal of the sample therein, and       B. acuator means for seq-entially lowering first the sleeve and the the piston so as to isolate and remove a sample of liquid.   
     
     
       2. A device according to claim 1 wherein the inlet and outlet in the cylindrical body are transversely orientated. 
     
     
       3. A device according to claim 1 wherein the actuation of the sleeve and piston in a sequential manner is achieved by a pneumatic actuator. 
     
     
       4. A device according to claim 1 wherein a single stroke by the actuator means is converted into a differential action by means of a compression spring acting between the sleeve and the piston so as to form a lost-motion mechanism. 
     
     
       5. A device according to claim 4 wherein the compression spring is located between collars attached to the sleeve and the piston. 
     
     
       6. A device according to claim 5 wherein in a normal open position of the body inlet and outlet, the sleeve and the piston are held in position above the inlet and outlet by means of a cage engaging with the sleeve and lifting the sleeve so as to compress the spring against the piston, the piston being restrained from upward movement by means of a stop member on the upper portion of the outer body. 
     
     
       7. A device according to claim 1 wherein the non-return valve in the piston is retained in a closed position by means of a spring. 
     
     
       8. A device according to claim 7 wherein the non-return valve is provided with an elongated valve stem extending through the length of the piston so as to form an internal annulus within the piston. 
     
     
       9. A device according to claim 1 wherein the sample removal means comprises a relief valve. 
     
     
       10. A device according to claim 9 wherein the relief valve is externally placed with respect to the outer cylindrical body. 
     
     
       11. A device according to claim 10 wherein a shut-off valve is provided between the inside of the piston and the relief valve. 
     
     
       12. A device according to claim 1 wherein both the non-return valve and the piston are removably mounted. 
     
     
       13. A device according to claim 1 wherein the body inlet is provided with a flow straightening mouthpiece. 
     
     
       14. A device according to claim 1 wherein the actuation of the sleeve and piston in a sequential manner is achieved by an electrical actuator. 
     
     
       15. A device according to claim 1 wherein the actuation of the sleeve and piston in a sequential manner is achieved by a hydraulic actuator. 
     
     
       16. A device according to claim 4 wherein the compression spring is located between shoulders formed on the sleeve and the piston. 
     
     
       17. A device according to claim 5 wherein in a normal open position of the body inlet and outlet, the sleeve and the piston are held in position above the inlet and outlet by means of a yoke engaging with the sleeve and lifting the sleeve so as to compress the spring against the piston, the piston being restrained from upward movement by means of a stop member on the upper portion of the outer body.